\section{Concepts and Background}
\label{section:background}

\subsection{Reputation}

1) Feedback

As depicted by Fig. \ref{} (\textit{well we have to put a figure there :-)}) our conception of feedback is divided in two types:
\begin{itemize}

\item Objective feedback corresponding to the monitoring information provided during and at the end of service execution, in respect of the SLA.

\item Subjective feedback corresponding to the evaluation of service provided by the customers. 

\end{itemize}

2) Credibility

\subsection{Provenance}

''Provenance, i.e., the origin or source of an object, is becoming an important aspect since it offers the means to verify data products, to infer quality and to analyse the processes that led to them and to decide whether they can be trusted''  \cite{DBLP:journals/ftweb/Moreau10}. 

In this section, we give a description of the fundamental elements of both provenance and provenance awareness for services and service-based systems and then for PROV model \cite{w3c-prov-primer} in particular. The latter has formed the basis on which we have extended the ServiceProv Ontology, as this can be found on-line at \textsf{https://sourceforge.net/projects/serviceprov/files/service\-prov\#}. The latter forms a provenance data schema for service-based systems taking into consideration different different provenance aspects through the service life cycle such as the the provenance of service execution, service discovery and selectio, service orchestration and choreography, service aggregation and at last provenance of QoS and Resources. A detailed definition of each concept and property of this ontology is provided at \url{https://sourceforge.net/projects/serviceprov/files/serviceprov.pdf}.

''Provenance covers the data about entities, activities, or people involved in the process that produced a data item or thing \cite{w3c-prov-primer}'' with the purpose to understand how data was collected, to determine ownership and rights over the data object or to verify that the process and steps used to obtain the data result complies with given requirements. We can consider provenance to represent the `origin' or `source' of a digital object \cite{w3c-prov-primer}.
 
 PROV is W3C's specification to express provenance records, which contains descriptions of the entities and activities involved in producing and delivering or otherwise influencing a given object
\cite{w3c-prov-primer}. As people may see provenance from a different perspective, PROV specification covers different types of information that may be captured in provenance records corresponding to the primary concepts of the W3C PROV's notation; namely \emph{entities}, \emph{activities} and \emph{agents} and \emph{events}. 

\textsf{Activities} represent processes that have occurred over a period of time and act upon entities. 

\textsf{Entities} are digital, physical or conceptual things with some fixed \emph{values}, that existed. Activities \emph{generated} new entities and \emph{used} existing entities, and one entity
may have been \emph{derived} from another. 

\textsf{Agents} denote something that was responsible for an activity having taken place. PROV also allows us to express the \emph{role} played by an entity or agent in an activity, the \emph{time} at which an entity was generated or used by an activity, the \emph{plan} that was followed by an activity in execution and much more. PROV also introduces a number of expanded terms such as \textit{collection}, which denotes an entity that provides a structure to some constituents (\emph{members}), or \emph{instantaneous events} that denote transitions in the world. 

\textsf{Events} include \emph{generation}, \emph{usage}, or \emph{invalidation} of entities, as well as \emph{start} or \emph{end} of activities. 


 W3C PROV has built PROV ontology~\cite{w3c-prov-o}, an OWL2\cite{owl2-overview} ontology which allows mapping of the PROV data model to RDF \cite{rdf}. PROV-O defined a set of classes and properties along with restrictions on them to represent the provenance information which is generated or collected for different systems executing under different contexts. This ontology gives the opportunity for extensibility and specialisation of its concepts to create new domain concepts falling into specific application contexts. We have previously done so by extending this into \textsf{Service Prov Ontology} for representing provenance of services and more specifically composite services. 
 
 Yet, in the context of this research we extend the \textsf{ServiceProv} Ontology with concepts that will allow to represent the provenance of feedbacks for atomic and composite services. We present a more detailed definition of these concepts and how these interwork and merged with concepts of the SLA ontology \textit{{maybe you should refer before a bit to your SLA ontology}} in order to provide a means for evaluating services in Sect. \ref{section:approach}.
 
 
 
\subsection {Provenance of Feedback}

\textit{Kahina - Do we need a separate section to define this? Or do you think we should define a bit better the provenance (of feedback) in our context in the previous paragraph? Otherwise we can talk about that in the section you have made in IV approach - A. Purpose of Feedback provenance. What do you think?}

\textit{Do you think the (why provenance) is interesting for the feedbacks? By (why provenance)  I mean to identify tuples in our ontologies whose presence justifies a query result? Do we look into querying our ontological models or just building an ontological design to represent those? This question came up as I was writing the section on the provenance concepts about feedback. I mean in order to say that the provenance of feedback is meaningful for the credibility/validation of this, we should probably say that we build this ontological design in order to allow querying of our ontology when the latter populated with instances about the provenance of objective and subjective feedback. We should also consider maybe that when we will try to clarify the different kinds of links between the two ontologies. Tell me what you think about this idea or if I am getting out of context. }

